ON THE STRUCTURE OF THE TRAILING VORTICES AROUND RUSHTON TURBINE-BLADES

An experimental study of the structure of the trailing vortices formed around the blades of Rushton turbines in stirred reactors has been ca rried out. Time-resolved and angle-resolved (ensemble-averages over 1- degrees of revolution) measurements of the velocity variation were obt ained by laser-Doppler anemometry by synchronising the velocity data w ith the rotation of the impeller shaft. The measurements quantify the mean flow and the kinetic energy of turbulence in the vortices and sho w that ensemble-average measurements of the flow over 360-degrees of r evolution can overestimate the turbulence fluctuations by up to 400%. The results are suitable for use as boundary conditions in CFD calcula tions of the rotating flows around the impeller and for the validation of rotating-frame predictions of the flowfield.